1. Field of the Invention
The present invention relates to monitoring devices and monitoring methods, and in particular, it relates to a monitoring device and a monitoring method used when a data held in the memory of a target device is monitored in real time.
2. Description of Related Art
In recent years, the highly functional progress in semiconductor integrated devices has been remarkable. In addition, the importance of performing a high-precision verification of the operation of hardware or software in a verification target device has been increased.
At the time of the operation verification of hardware or software in the verification target device (hereinafter, referred to as target device appropriately), in general, a tool called as an emulator is used. The emulator emulates the function of a microprocessor (CPU (Central Processing Unit) of the target device, thereby to realize the operation verification of the target device.
Japanese Patent Laid-Open No. 06-290073 discloses a monitoring device for monitoring storage contents of a memory portion of an electronic control unit.
In FIG. 11 is shown a schematic configuration of the monitoring device disclosed in Japanese Patent Laid-Open No. 06-290073. As shown in FIG. 11, an electronic control unit 100 is connected with a monitoring device 101 through a cable 105. A DPRAM (Dual Port Random Access Memory) 109 of the monitoring device 101 is written with the same data as the date held in a RAM (Random Access-Memory) 102 of the electronic control unit 100. Consequently, by analyzing the data held in the DPRAM of the monitoring device 101, the operation of the electronic control unit 100 as the target device can be verified.
Now, to verify the operation of the target device with high accuracy, during the operation of the target device, it is necessary to sequentially acquire and analyze the date held in a semiconductor storage device (hereinafter, referred to as memory appropriately) of the target device. When the monitoring device is used, accompanied with the sequential renewal of the data held in the memory of the target device, the data held in the memory of the monitoring device for holding the same data as the data held in the memory of the target device is also sequentially renewed.
The present inventor has recognized that, when a memory having two ports of a data input port and a data output port is built-into the monitoring device and the data held in the memory is monitored to verify the data held in the memory in real time during the operation of the target device, a problem arises that there arises an overlapping period between a data writing period to the memory of the monitoring device and a data reading period from the memory of the monitoring device. For example, during the period when the data is read from the memory of the monitoring device, when the data held in the memory of the monitoring device is also renewed accompanied with the renewal of the memory of the target device, it is often the case that the data read from the memory of the monitoring device does not precisely reflect the data held in the memory of the target device at a certain point. As a result, to verify the operation of the target device with high accuracy becomes difficult.
As described above, it has been often the case that the data writing period to the memory of the monitoring device and the data reading period from the memory of the monitoring device overlap and the securement of the reliability of the data read from the memory of the monitoring device becomes difficult.